1. Field of Invention
This invention relates to the inspection of geometrically symmetrical stable units such as buttons and particularly to the inspection of the central zone of buttons for manufacturing defects.
2. Description of the Prior Art
When buttons are manufactured, threadholes or eyes are placed in the central zone of the button. Not all of the holes or eyes are perfectly formed. Sometimes a hole may be plugged with a flash or web of material; the holes may be improperly spaced or may be entirely missing. Buttons with such defects are unacceptable for use on garments. In addition, since the buttons are fastened to the garments by automatic machinery these defects can cause a breakdown in the button-fastening machinery resulting in downtime of the machinery causing a loss of productivity. In order to avoid these losses, button manufacturers have had to inspect the buttons after manufacture.
Generally the buttons are inspected manually by a group of workers who watch the buttons pass on a moving conveyor. If a defective button is spotted, it is manually lifted from the conveyor. This work is necessarily very tedious. Not only is it tedious but it is also expensive in terms of time and money and due to the very nature of the work it is very inefficient.
Various schemes to automatically inspect buttons have been proposed, such as that shown in U.S. Pat. No. 3,956,636. A button inspecting system employing laser technology and computers has been proposed. While such a method could conceivably provide a reliable inspection, the cost of the lasers and the maintenance of the computers has made such a system of doubtful commercial practicality. Notwithstanding these various proposals to automate the inspection, today the manual method of inspection is widely employed.
Accordingly, it is an object of the present invention to provide a highly reliable and efficient method and apparatus for the inspection in sorting of buttons. It is a further object of this invention to provide a relatively inexpensive method and apparatus for the inspection and sorting of buttons.